If you really want Airpoints
One thing that you should also consider is Flybuys.
You cannot directly transfer Flybuys points into NZ Airpoints unless you have a BNZ GlobalPlus card. Flybuys is free to you and you can double dip by going to a Flybuys retailers, getting Flybuys points (variable earn depending on retailer) and using your GlobalPlus cards. Flybuys transfers 6 points to 1 NZ Airdollar or if you do not have the BNZ card it is 7 Flybuys points to the equivalent 1 NZ Airdollar for a flight redemption. BNZ also has a Airpoints earning home loan, not worth it as you pay a higher interest rate that exceeds the dollar value of an Airdollar.
Unless your *A program gives you a minimum miles guarantee then crediting NZ domestic flights to the NZ scheme is the best value, also there are some secret good earners for NZ Airdollars out there.